Difference Between Agile and Waterfall: Software Development Methodologies

agile vs waterfall illustration

At the beginning of any software project, teams and organizations have to first deal with the question of Agile vs. Waterfall. Software projects follow a methodology of clearly defined processes or software development life cycle (SDLC) to ensure the end product is of high quality. An SDLC identifies phases and the structured flow from one phase to another phase. Typically, there are six to seven phases. Agile and waterfall are two popular, but very different, development processes.

Waterfall project management is a traditional model for developing engineering systems and is originally based on manufacturing and construction industry projects. When applied to software development, specialized tasks completed in one phase need to be reviewed and verified before moving to the next phase. It is a linear and sequential approach, where phases flow downward (waterfalls) to the next.

Agile methodology is a type of incremental approach to software development based on principles that focuses more on people, results, collaboration, and flexible responses to change. Instead of planning for the whole project, it breaks down the development process in small increments completed in iterations, or short time frames. Each iteration includes all SDLC phases such that a working product is delivered at the end. After several iterations, a new or updated product is released.

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Differences Between Agile vs. Waterfall

Both methodologies can help developers produce high-quality project management. Depending on the specific project requirement, knowing the difference between agile and waterfall can better equip a development team to choose the right process and methods in delivering a successful software project. Some of the distinct differences are:

  • Agile is an incremental and iterative approach; Waterfall is a linear and sequential approach.
  • Agile separates a project into sprints; Waterfall divides a project into phases.
  • Agile helps complete many small projects; Waterfall helps complete one single project.
  • Agile introduces a product mindset with a focus on customer satisfaction; Waterfall focuses on successful project delivery.
  • Requirements are prepared everyday in Agile, while requirements are prepared once at the start in Waterfall.
  • Agile allows requirement changes at any time; Waterfall avoids scope changes once the project starts.
  • Testing is performed concurrently with development in Agile; testing phase comes only after the build phase in a Waterfall project.
  • Test teams in Agile can take part in requirements change; test teams in Waterfall do not get involved in requirements change
  • Agile enables the project team to operate without a dedicated project manager; Waterfall requires a project manager who plays an essential role in every phase.

What Is Agile Development?

Agile development is a team-based approach that emphasizes rapid deployment of a functional application with a focus on customer satisfaction. It defines a time-boxed phase called a sprint with a defined duration of two weeks.

At the start of each sprint, a list of deliverables are prioritized based on customer input. At the end of the sprint, the developers and the customer review and evaluate the work with notes for future sprints. As a methodology based on general principles, more specific methods based on processes such as Scrum and Kanban are called types of agile methodology.

What Are the Benefits of Agile?

Some of the known benefits of an agile project are:

  • Faster software development life cycle
  • Predictable schedule in sprints
  • Customer-focused approach, resulting in increased customer satisfaction
  • Flexible in accepting changes
  • Empowers teams to manage projects
  • Promotes efficient communications
  • Ideal for projects with non-fixed funding

What Are the Disadvantages of Agile?

The following are disadvantages of agile:

  • Agile requires a high degree of customer involvement, which not all customers are comfortable with or prefer to give.
  • Agile assumes every project team member is completely dedicated, without which weakens the principle of self-management.
  • A time-boxed approach may not be enough to accommodate all deliverables, which will require changes in priority and additional sprints that can bring up cost.
  • Agile recommends co-location for efficient communication, which is not always possible.

What Is the Waterfall Development Process?

Waterfall project management is a sequential approach that divides the SDLC to distinct phases such as requirements gathering, analysis and design, coding and unit testing, system and user acceptance testing, and deployment. The next phase can only proceed if the previous phase has been completed. In between phases, a deliverable is expected or a document is signed off.

All phases are passed through and completed only once, so all requirements are gathered as much as possible at the start to provide the information in creating the plans, schedules, budget, and resources. It is plan-driven, so any changes after the project has started would offset the original plan and require a restart.

What Are the Benefits of Waterfall?

The following are the benefits of waterfall methodology:

  • Straightforward planning and designing due to the agreement on deliverables at the start of the project.
  • Better design with whole-system approach
  • Defined scope of work
  • Easier costing
  • Clear measurements of progress
  • Defined team roles
  • Dedicated resources can work in parallel for their specific tasks

What Are the Disadvantages of Waterfall?

Newer development methodologies were created because of known disadvantages of waterfall, including:

  • Rigid structure to allow necessary changes
  • No allowance for uncertainty
  • Limited customer engagement, resulting in poor satisfaction
  • Sequential approach is not ideal for a large-sized project where the end result is too far in the future
  • Testing is done only at the latter phases of the project.

A better way to approach a software development project is to focus first on your business goals. Then teams can choose, adapt, and even customize to create the best hybrid methods fit for their needs.

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Jose Maria Delos Santos

Jose is a subject matter expert and member of the writing team for Project-Management.com and Bridge24. He has written hundreds of articles including project management software reviews, books reviews, training site reviews, and general articles related to the project management industry.